System for evacuating detached tissue in continuous flow irrigation endoscopic procedures

ABSTRACT

A continuous flow irrigation endoscope and a continuous flow irrigation fluid management system, both designed to be compatible to each other and to function as a single system. The endoscope and the fluid management system are synergistic to each other such that both enhance the efficiency of each other. The invented system allows a body tissue cavity to be distended by continuous flow irrigation so that detached tissue pieces and waste fluid present inside a body tissue cavity are continuously automatically evacuated from the tissue cavity without causing the cavity to collapse at any stage and without the need of withdrawing the endoscope of a part of the endoscope from the tissue cavity. No type of feedback mechanism, such as mechanical or electrical, or valve or valve like systems, are incorporated in the endoscope to influence or facilitate the removal of detached tissue pieces or waste fluid in any manner.

The present application claims the benefit of Indian Provisional PatentApplication No. 2237/DEL/2006, filed on Oct. 11, 2006, the entiredisclosure of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to surgeries and, in particular, toendoscopic procedures which deploy continuous flow irrigation, such ashysteroscopic fibroid morcellation, trans uretheral prostatemorcellation, hysteroscopic polyp morcellation, hysteroscopicseptoplasty, hysteroscopic adhesiolysis, trans uretheral morcellation ofbladder tumors, arthroscopy, and endoscopic procedures of the brain andspine.

BACKGROUND OF THE INVENTION

Continuous flow endoscopes are frequently used in endoscopic proceduressuch as hysteroscopy, trans uretheral urologic endoscopic procedures andarthroscopy. Those skilled in the art would know the structuralcomposition of a continuous flow irrigation endoscope. In thisapplication, the term “continuous flow irrigation” means that fluidsimultaneously enters and escapes from a tissue cavity via separateentry and exit points, as a result of which positive fluid pressure iscreated inside the tissue cavity which distends the cavity. A continuousflow irrigation endoscope generally comprises an inner sheath which isplaced inside the cylindrical lumen of an outer sheath. The sheaths arehollow cylindrical tubes which have a distal end which enters a tissuecavity, and a proximal end on which an inflow or outflow port isattached for the purpose of instilling or evacuating fluid from thecavity. The irrigation fluid is instilled via an inflow port.

In many prior art systems the instilled fluid travels through the lumenof the inflow sheath and enters the tissue cavity via the distal openingof the inflow sheath. The waste fluid present inside the tissue cavityenters into a potential space present between the outer and the innersheaths via multiple holes present near the distal end of the outersheath and this waste fluid is finally evacuated via the outflow portattached at the proximal end of the outer sheath. A fiber optictelescope is placed inside the cylindrical lumen of the inner sheath toview the interior of the tissue cavity. An endoscopic instrument canalso be introduced via the lumen of the inner sheath. In this paragraph,the terms “outer sheath” and “inner sheath” refer to hollow cylindricaltubes which participate in maintaining the structural integrity of theendoscope, and such tubes also cannot move relative to each other. Also,the endoscopic instrument frequently moves relative to the outer and theinner sheaths. Various different types of “continuous flow irrigationendoscopes” have been described in U.S. Pat. Nos. 3,835,842; 5,320,091;5,392,765; 5,807,240; and U.S. Patent Appln. Publ. Nos. 2003/0130565 A1(Jul. 10, 2003); 2006/0041186 A1 (Feb. 23, 2006); and 2006/0122459 A1(Jun. 8, 2006).

The arrangement described in the preceding paragraph has two majordisadvantages which are negated by the system of the proposed invention.The disadvantages are as follows:

One disadvantage is that detached tissue pieces, larger than a criticalsize, present in the tissue cavity are unable to pass through thepotential space between the outer and the inner sheaths. Thus, inendoscopic procedures the entire endoscope or the “endoscopicinstrument” has to be repeatedly removed from the tissue cavity in orderto evacuate the detached tissue pieces present inside the tissue cavity,and this increases the risk of complications like perforation, excessivebleeding and also increases the surgical time. As described in EP0996375, U.S. Pat. No. 7,249,602 and U.S. Patent Appln. Publ. No.2006/0047185, it may be argued that, instead of one outflow port, twooutflow ports be installed via suitable mechanical means at suitablelocations in the endoscope, one outflow port for primarily evacuatingthe waste fluid from the cavity and the other outflow port being meantto primarily evacuate the resected or cut tissue. However, such anarrangement is not desirable since it necessitates the incorporation oftwo out flow channels instead of one and it also tends to increase theoverall weight of the endoscope. The system of the present inventionsolves all the problems described in this paragraph by utilizing onlyone single outflow port, attached to a single outflow channel, whichserves to evacuate both detached tissue pieces and waste fluid from thetissue cavity in a continuous irrigation manner.

The other disadvantage is that the inner sheath by virtue of occupyingadditional space reduces the effective lumen diameter of the endoscopewhich necessitates a reduction in the thickness or size of the“endoscopic instrument” or the telescope or both. The system of theproposed invention reduces the problem mentioned in this paragraph byutilizing only one housing sheath and by utilizing special type ofendoscopic instrument which additionally also functions as the soleoutflow channel for simultaneously removing waste fluid and detachedtissue pieces. In U.S. Pat. No. 6,824,544, waste fluid and tissue piecesare evacuated via an inflow sheath and the tissue is resected by aseparate endoscopic instrument, loop, which cannot participate inremoval of waste fluid or tissue pieces; both these features beingcontrary to the principals of the present invention.

Also, unlike U.S. Pat. No. 6,824,544, in the present invention, a singleoutflow channel (that is suction channel) is not bifurcated at the levelof the endoscope and any type of valve, simple or solenoid operated, isnot attached to the outflow channel. Also, unlike U.S. Pat. No.6,824,544, in the present invention, a controller is not used forinfluencing or regulating the working of the endoscope, for example byway of controlling the opening and closing motion of solenoid valves.This paragraph describes requirements which essentially need to befulfilled by the system of the present invention. These requirementshave been imposed so that the use of the invented endoscope is notrestricted to any specific type of fluid management system with acontroller, so that only one outflow tube is needed to be connected tothe endoscope, such that the endoscope is simple, light and userfriendly.

In the present invention, the diameter or area of cross section of theinner lumen of a single outflow port needs to be at least equal to thediameter or area of cross section of the outflow channel, so thatdetached tissue pieces and waste fluid could be evacuated in the mostefficient manner. Thus, in the present invention, unlike in EP 0996375,U.S. Pat. No. 7,249,602 and U.S. Patent Appln. Publ. No. 2006/0047185, avalve is not attached to the outflow channel for controlling thepressure or the fluid flow.

The present invention is essentially a continuous flow irrigationendoscope which cannot function if the single outflow channel isblocked, for example by an opening or closing valve. Thus, in thepresent invention, unlike in EP 0996375, U.S. Pat. No. 7,249,602 andU.S. Patent Appln. Publ. No. 2006/0047185, an opening or closing valveis not attached to the outflow channel.

The detached tissue pieces, especially the large size ones, can beevacuated by continuous flow irrigation only if the outflow channel andoutflow port of the endoscope have a substantially large lumen diameter.But the same could cause the cavity to collapse intermittently during anendoscopic procedure because the “large lumen diameter” would promotethe pressurized irrigation to be expelled out of the tissue cavity via alarge bore outflow port. Such problem has been solved by attaching aspecially designed endoscope to a specially designed fluid managementsystem, the resultant arrangement being the system of the presentinvention.

OBJECT OF THE INVENTION

One object of the invention is to provide a continuous flow irrigationsystem, comprising an endoscope and a fluid management system, in whichthe detached tissue pieces and/or waste fluid present inside a tissuecavity are evacuated automatically in a continuous manner from thetissue cavity without causing the tissue cavity to collapse at any givenmoment of time.

Another object of the invention is to provide a continuous flowirrigation system, comprising an endoscope and a fluid managementsystem, in which the detached tissue pieces present inside a tissuecavity are evacuated automatically in a continuous manner from thetissue cavity without the need of removing the entire endoscope or apart of the endoscope from the tissue cavity.

Another object of the invention is to provide a continuous flowirrigation system, comprising an endoscope and a fluid managementsystem, in which both the detached tissue pieces and waste fluid aresimultaneously evacuated automatically in a continuous manner from thetissue cavity via a same single outflow port connected to a singleoutflow channel.

Another object of the invention is to provide a continuous flowirrigation system, comprising an endoscope and a fluid managementsystem, in which both the detached tissue pieces and waste fluid aresimultaneously evacuated automatically in a continuous manner from thetissue cavity via a same single outflow port, such that no mechanical orelectrical feedback mechanism or any type of valve system is utilizedfor evacuating the detached tissue pieces or waste fluid.

Another object of the invention is to provide a continuous flowirrigation endoscope system to which only a single outflow tube needs tobe connected.

Another object of the invention is to provide a continuous flowirrigation endoscope system in which the diameter or area of crosssection of the inner lumen of the outflow port is at least equal to thediameter or area of cross section of the outflow channel.

Another object of the invention is to provide a continuous flowirrigation system in which the endoscope is relatively light in weight.

Another object of the invention is to provide a continuous flowirrigation system which is user friendly, safe and efficient.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a continuous flow irrigation endoscope, afluid management system employing such an endoscope, and a method ofendoscopic surgery. A continuous flow irrigation endoscope and acontinuous flow irrigation fluid management system, both designed to becompatible to each other, function as a single system. The endoscope andthe fluid management system are synergistic to each other such that bothenhance the efficiency of each other. The invented system allows a bodytissue cavity to be distended by continuous flow irrigation so thatdetached tissue pieces and waste fluid present inside a body tissuecavity are continuously automatically evacuated without causing thecavity to collapse at any stage, and without the need of withdrawing theendoscope of a part of the endoscope from the tissue cavity.

The endoscope has only a single housing sheath without an inner sheath.

The fluid management system comprises an inflow pump and an outflow pump(for example, an inflow peristaltic pump and an outflow peristalticpump) which work simultaneously, for indefinite time, at fixed flowrates to create and maintain any desired cavity pressure for any desiredcavity flow rate. The inflow pump is connected to an inflow port of theendoscope, while the outflow pump is connected to an outflow port of theendoscope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the system of the present inventioncomprising an endoscope attached to a fluid management system.

FIG. 2 shows the endoscope of FIG. 1.

FIG. 3 is similar to FIG. 1, except that, in this figure, a tissuecavity has been substituted in place of the endoscope.

FIG. 4 is similar to FIG. 3, except that, in this figure, a controlleris not included.

FIG. 5 shows the inflow part of the fluid management system along withthe inflow peristaltic pump 5, the pressure transducer 17 and theconstriction site 8.

FIG. 6 is similar to FIG. 4, except that, in this figure, a shaded arearepresents a region having an almost similar pressure.

FIG. 7 is similar to FIG. 2, except that, in this figure, anadditional/optional constriction site housing tube 15 and anadditional/optional pressure transducer 26 have been included.

DETAILED DESCRIPTION OF THE INVENTION

The system of the present invention comprises an endoscope and a fluidmanagement system, both designed especially for each other. Theendoscope and the fluid management are both based on the principles ofcontinuous flow irrigation, as both work together as one unit toevacuate detached tissue pieces and waste fluid from a tissue cavity inendoscopic procedures which deploy continuous flow irrigation andwithout the necessity of withdrawing the endoscope or a part of theendoscope from the tissue cavity.

For easy understanding, the endoscope and the fluid management systemshall be described separately, followed by a description of both of themtogether.

The Endoscope

The present invention relates to a continuous flow irrigation endoscopein which detached tissue pieces and waste fluid present inside a tissuecavity are automatically evacuated in a continuous manner withoutwithdrawing the endoscope or any part of the endoscope from the tissuecavity.

The basic layout of the invented endoscope is shown in FIG. 2. Theendoscope 27 has a distal end 28 which enters a tissue cavity and aproximal end 29 which lies outside the tissue cavity. The inventedendoscope comprises an externally located “housing sheath” 30, anoptical system 31 and a hollow cylindrical tube like instrument 32.

Again referring to FIG. 2, unlike many prior art systems, the endoscopeof the present invention does not have a separate inner sheath, butrather a single sheath termed as housing sheath 30. The housing sheath30 has an inflow port 33 located near its proximal end 29. Sterileirrigation fluid for distending a body tissue cavity is instilled viathe inflow port 33 in the direction of the arrow 34. The irrigationfluid travels through the lumen 35 of the housing sheath 30 and finallyenters the tissue cavity via a distally located opening 36 of thehousing sheath 30. The cross section of the distally located opening 36and/or the cross section of the housing sheath 30 could also be oval inshape, and could also have additional configurations.

Again referring to FIG. 2, a hollow cylindrical tube like instrument 32is located inside the lumen 35 of the housing sheath 30. For brevity,the hollow cylindrical tube like instrument 32 shall be referred to asinstrument 32. The instrument 32 is a hollow cylindrical tube likestructure having a distal opening 40, a lumen 41 and a proximallylocated opening which is being termed as the outflow port 42. The lumendiameter of the outflow port 42 is the same as the lumen diameter of therest of the instrument 32. The lumen diameter of the outflow port 42could also be less than the lumen diameter of the rest of the instrument32, but such an arrangement could tend to retard the evacuation ofdetached tissue pieces. The waste fluid and the detached tissue piecespresent inside the tissue cavity enter the lumen 41 of the instrument 32through the distal opening 40 and travel in the direction of the arrow43. The waste fluid and the detached tissue pieces are finally evacuatedvia the outflow port 42. Depending upon the surgical requirement thecross section of lumen 41 could also be oval or of any other shape.

The effective cross sectional area of the housing sheath 30 should bepreferably less than the effective cross sectional area of theinstrument 32, as such an arrangement would facilitate the evacuation ofdetached tissue pieces. Here, the term “effective cross sectional area”of the housing sheath 30 relates to the total cross sectional area ofthe housing sheath 30 from which the cross sectional area occupied bythe instrument 32 and the optical channel 39 has been subtracted. Thecross sectional area of the instrument 32 is denoted by the crosssectional area of the lumen 41 of the instrument 32.

The instrument 32 is placed inside the housing sheath 30 by virtue of afluid tight contact. Also, those skilled in the art would know that,generally, an obturator is inserted inside the housing sheath subsequentto which the housing sheath is inserted into a tissue cavity. However,the obturator assembly has not been included in the drawing only for thesake of simplicity.

Again referring to FIG. 2, the optical system 31 comprises a telescopeeyepiece 38 which is connectable to a video camera, an optical channel39 which contains fiber optic bundles and a distal viewing tip 37 forvisualizing the interior of the tissue cavity. The optical channel 39 isnot straight and has been deliberately provided with a bend 44. Theoptical channel 39 and the bend 44 are placed inside the lumen 35 of thehousing sheath 30 and outside the lumen 41 of the instrument 32. In casethe bend 44 is placed outside the lumen 35 of the housing sheath 30,then the fragile optical channel 39 could easily break at the bend 44.The bend 44 has been included to provide additional space for theinstrument 32, especially if the instrument 32 were to be ahysteroscopic or urologic morcellator, or an arthroscopic shaver inwhich cases additional space is needed to accommodate the drivingmechanism of the morcellator or the shaver. The optical channel couldalso be straight, but such an arrangement may not allow theincorporation of the said morcellator or a shaver. Also, the lightsource arrangement for the optical system 31 has not been included inFIG. 1 for simplicity.

Again referring to FIG. 2, the instrument 32 could be morcellator forhysteroscopic fibroid resection or for cutting a prostate adenoma inurologic endoscopic procedures. The instrument 32 could also be a shaverto be used in arthroscopic surgeries. The morcellator or the shaver havenot been separately shown in any of the figures but the hollow innerchannels of both are represented by the lumen 41 of the instrument 32.Also, those skilled in the art would understand that a window openingcorresponding with the distal opening 40 is present near the distal endof hysteroscopic morcellators and shavers, wherein two cutting edgesincorporated in two rotatable tubes facilitate tissue cutting in theregion of the said window. If the window is kept in the open positionwhile the morcellator or the shaver is not operating, then the samewould allow continuous flow irrigation all through the endoscopicprocedure that is even while the morcellator or shaver is nonfunctional. The instrument 32 could also be a simple cutting knifewherein the distal end of the instrument 32 would be required to beshaped like a conventional knife. The knife could also function as amonopolar electrosurgical instrument. The instrument 32 could also be anelectrode such as a ball electrode for ablating the endometrium, aprostate adenoma or a bladder tumor. The ball electrode, unlike theprior art ball electrodes, would have centrally placed a hollowcylindrical channel via which waste fluid and detached tissue generatedduring ablation could be evacuated.

Again referring to FIG. 2, it is important to note that instrument 32should be essentially capable of moving in a to and fro directionrelative to and parallel to the long axis of the housing sheath 30. Inadditional embodiments, the instrument 32 is also capable of rotatingaround the long axis of the instrument 32 in either direction. Suitablemechanical means are deployed to facilitate the to and fro, and therotary, movements of the instrument 32. The distal opening 40 of theinstrument 32 may also be cut obliquely such that opening 40 is ovalinstead of being round.

Again referring to FIG. 2, the proximal part of the instrument 32 couldalso be provided with a bend like the bend 44 provided in the opticalchannel 39, and such bend could be located inside or outside the lumen35 of the housing sheath 30. However, such an arrangement could retardthe evacuation of detached tissue pieces.

Referring to FIG. 2, the relative locations of the optical channel 39and of the instrument 32 could even be interchanged with respect to eachother or with respect to the inflow port 33.

Referring again to FIG. 2, the entire instrument 32, from the distalopening 40 to the proximally located outflow port 42, may comprise, forexample, a metal, a rigid plastic material, a ceramic material, or acombination of these materials.

Also, the outlet of instrument 32 has been termed as outflow port 42only for an easier description. In the prior art continuous flowendoscopes, the term outflow port is commonly referred to an outletattachment which is attached at the proximal end of an outer or an innersheath. Also, in the prior art systems the sheaths are immovablerelative to each other, they do not function as an instrument, theirpurpose being only to provide structural integrity to the endoscope andto provide channels for instilling or removing fluid from a tissuecavity. However, in the present invention the so-called outflow port isattached at the proximal end of a movable instrument 32, the instrumentnot being meant to impart structural integrity to the endoscope, and thesaid instrument can also be replaced by a different type of instrumentdepending upon the surgical requirement.

Referring to FIG. 2, it is important to note that no feedback mechanism,no valves, and no valve like system have been provided anywhere in theendoscope 27 for facilitating or influencing the evacuation of detachedtissue pieces and waste fluid in any manner, or otherwise. It isimportant to note that the proximal end of the instrument 32 has notbeen bifurcated in any manner. This implies that the outlet port 42 isconnectable to only a single outflow tube which would transport thedetached tissue pieces and the waste fluid to a waste collectingcontainer. The outflow tube may be made of flexible resilient polymericmaterial. If at all any bifurcation, valve system or a feedbackmechanism, as explained in this paragraph, needs to be installed thenthe same could be installed only in the outflow tube, sufficiently awayfrom the endoscope 27, such that the installation does not enhance theweight of the endoscope because low weight of the endoscope is one ofthe objectives of the invention.

Also in the preceding paragraphs it might be misinterpreted that theinstrument 32 is primarily meant to act as an outflow channel forevacuating waste fluid and detached tissue pieces from a tissue cavity.However, the primary aim of the instrument 32 is to act as an endoscopicinstrument while the hollow cylindrical lumen 41 of the instrument 32simply provides a passage for the evacuation of detached tissue piecesand waste fluid.

The outflow port 42 of endoscope 1 has a relatively large lumen diameterand the same could cause the pressurized irrigation fluid present insidethe tissue cavity to be intermittently expelled via the large boreoutflow port 42. This intermittently would cause the tissue cavity tointermittently collapse during an endoscopic procedure, which could leadto surgical complications like perforation and bleeding. To solve thisproblem, it is recommended that the endoscope 27 be used with aspecially designed fluid management system which would not allow thetissue cavity to collapse and would also provide additional benefits.Such a fluid management system is described in the subsequentparagraphs.

The Fluid Management System

The fluid management system described in the subsequent paragraphs isrecommended to be used with the endoscope described in the previousparagraphs. The fluid management system is a system for distending bodytissue cavities in endoscopic procedures. The proposed fluid managementsystem is meant to distend a body tissue cavity by continuous flowirrigation in such a manner that the cavity pressure is absolutelyindependent of the cavity outflow rate, such the both the cavitypressure and the outflow rate may be independently altered withoutvarying the value of the other parameter. For brevity, the fluidmanagement system shall be referred to as “system.”

The schematic diagram of the system is shown in FIG. 3. Two peristalticpumps 5 and 14 operate simultaneously to distend a tissue cavity in sucha manner that the cavity pressure is totally independent of the cavityoutflow rate. FIG. 3 represents the complete schematic diagram of the“system.” Please note that the controller being used in the system shownin FIG. 1 is an optional feature and the system would provide most ofthe features even without the controller. FIG. 4 represents theschematic diagram of the system but without a controller system. Thus,FIG. 4 is a mechanical version of the system. An operator, for example,a human operator, is required to operate such mechanical version of thesystem shown in FIG. 4. Though it is recommended that the controllerbased version of the system be used in endoscopic surgeries, it is notessential. The controller being used in the present system merelyassists the user in arriving easily at some of the additional functionswhich otherwise can be performed manually. Thus, in this application,the mechanical version of the system shown in FIG. 4 is discussed inmore detail to explain the basic physical principles of the system withgreater clarity.

Referring to FIG. 4, the system shown in this figure comprises twoperistaltic pumps which can maintain a predictably precise stable cavitypressure for indefinite time by working simultaneously at constantrotational speeds. Pump 5 pushes fluid into the cavity 18 and while pump14 simultaneously extracts fluid out of the cavity 18. The inlet end ofthe inflow peristaltic pump 5 is connected to a fluid source reservoir 1via tube 2. The distal open end of tube 2 is constantly submerged in asterile non viscous physiological fluid like 0.9% normal saline, 1.5%glycine, ringer lactate or 5% dextrose contained inside the reservoir 1at atmospheric pressure. One end of the tube 7 connects the “T junction”3 situated at the inlet end of the pump 5 while the other end of tube 7connects with the square junction 6 situated at the outlet end of thepump 5. The T junction 3 is thus the meeting point of three tubes,namely 2, 4 and 7. Similarly, the square junction 6 is the meeting pointof four tubes 4, 9, 7 and 10. The rollers of the peristaltic pump 5continuously compress and roll over the entire length of tube 4 thusdisplacing fluid in the direction of the curved arrow. This curved arrowdenotes the direction in which the rotors of the peristaltic pump 5rotate.

Tube 7 has a constriction point 8 which can be located anywhere alongits length. Such constriction point refers to a point where the innerdiameter of the lumen of tube 7 is reduced in comparison to the lumen ofthe rest of the tube 7. Such constriction may be a permanentconstriction in the lumen of tube 7 or it may be a variable constrictionwhose diameter may be increased or decreased as desired. A pressuretransducer 17 is attached at one of tube 9 while the other end of tube 9is connected anywhere on inflow tube 10. For practical convenience it isdesirable that the other end of tube 9 be connected in the up streampart of the inflow tube 10 such as at the square junction 6. Thepressure transducer 17 measures the fluid pressure via a column ofliquid or air present in the lumen of tube 9. The fluid pressure asmeasured by the pressure transducer shall be referred to as P. In thisapplication, the term “P” shall frequently be used to refer to theactual pressure inside the tissue cavity but in physical terms P is thepressure sensed by the transducer 17 at point 6. The pressure transducer17 may also be in the form of a membrane diaphragm incorporated in thewall of the inflow tube 10 such that this membrane diaphragm is indirect contact with the fluid contained in the inflow tube 10, such thatthe linear movement excursions of the said membrane are interpreted aspressure of the fluid inside the inflow tube 10 by a suitable pressuretransducer. Such type of pressure sensor being directly incorporated inthe wall of the inflow tube 10 senses the fluid pressure without theintervention of tube 9. The basic purpose of the transducer is tomeasure the fluid pressure inside the inflow tube 10, such as at point6, thus the mechanical construction of the transducer is not importantas long as it measures the fluid pressure. For simplicity, the existenceof tube 9 shall be continued to be considered in the rest of theapplication. The peristaltic pump 14 attached to the outflow sideactively extracts fluid out of the tissue cavity 18 via the out flowtube 12. The outlet end of the pump 14 is connected to a waste fluidcarrying tube 45 which opens into a waste fluid collecting reservoir 16at atmospheric pressure. The rollers of the pump 14 constantly compressand roll over the entire length of the peristaltic pump tubing 13, thusdisplacing fluid in the direction of the curved arrow which alsocorresponds with the direction of pump rotation.

To understand the system in a simpler manner, both pumps are beingconsidered to be identical in all respects and all the tubes are alsobeing considered to be having the same uniform inner diameter. However,the inner diameter of the tubes could also be different. Tubes 4 and 13consist of a soft resilient plastic material which can be efficientlycompressed by the rollers of the peristaltic pumps. The other tubes alsoconsist of a suitable resilient plastic material. It is assumed that allthe components shown in FIG. 4, including the two pumps, all tubes andthe cavity, are placed at the same horizontal height with respect to theground. Also, the rollers of pumps 5 and 14 should press adequately overtubes 4 and 13 so that there is no leak through these tubes when thepumps are stationary. It is also assumed that there is no abnormal leakof fluid in the irrigation system, for example leak via a accidentalhole made in any irrigation tube or a fluid leak which might occur ifthe endoscope loosely enters into the tissue cavity (for example, inhysteroscopic surgery, fluid leaks by the sides of the endoscope if thecervix is over dilated).

One end of the constriction site housing tube 7 instead of beingconnected with tube 2 at the T junction 3 can also open directly intothe fluid source reservoir 1. This shall not affect the efficiency ofthe system in any way but it may be practically difficult from thesurgical point of view in some special cases. Thus, such a provision isseparately shown in FIG. 7 and the tube has been labeled as 11 but ithas intentionally not been included in the main block diagram of thesystem in FIGS. 3 and 4 to keep the drawings simple. Also, aconstriction site housing tube similar to tube 7 labeled as 15 can beattached to the outflow tube 12 as shown in FIG. 7. In tube 15, theconstriction site is labeled as 25. Such tube can serve a number ofpurposes. Tube 15 can be utilized for relatively faster evacuation ofair bubbles from the cavity. In place of the adjustable constrictionsite 25, a pressure release safety valve may be incorporated as a safetyfeature, however it is more beneficial to install such pressure safetyvalve in the inflow circuit. The tube 15 may also be used for quicklyflushing air bubbles from the irrigation tubes by fully opening theconstriction site 25 for a few minutes or seconds. The tube 15 may alsobe used for any other purpose as deemed fit by the surgeon. However,tube 15 has intentionally not been included in the main block diagramsof the system because by including the tube 15 in the main blockdiagrams it would have become very difficult to explain the basicphysical principals of the system. However, tube 15 is a very beneficialcomponent and is thus recommended to be incorporated in the system. Theopening and closing of the constriction site 25 can also be regulatedmanually to help in various special advanced endoscopic applications.Incorporation of tube 15 with the variable constriction site 25 can helpin reducing the substantially high amplitude pressure variations insidethe cavity caused by abnormally large cavity wall contractions, but suchphenomenon is only rarely encountered. Also, an additional pressuretransducer 26 may also be attached on the out flow tube 12, if desired,as shown in FIG. 7. However, the pressure transducer 26 hasintentionally not been included in the main block diagrams of the systembecause, by doing so, it would be very difficult to explain the basicphysical principles of the system.

To clearly understand the system shown in FIG. 4, it is helpful todiscuss the functioning of the inflow peristaltic pump 5 as a separateentity as shown in FIG. 5. The rollers of pump 5 move in the directionof the curved arrow and squeeze over the entire length of peristalticpump tubing 4. Initially, tubes 2, 4, 7 and 9 contain air at atmosphericpressure and the free open end of tube 2 is submerged in a sterile fluidcontained inside the fluid source reservoir 1. The moment theconstriction site 8 is fully occluded, a column of fluid is immediatelysucked into tube 4 via tube 2, and thus fluid starts accumulating in theproximal parts of tubes 9 and 7. As the fluid fills in, tube 9 it pushesa column of air distal to the fluid column created in tube 9 and thepressure of this compressed air column is sensed by the pressuretransducer 17. The fluid pressure and the pressure of the compressed aircolumn are same, thus the pressure transducer 17 actually senses thefluid pressure. If tube 7 continues to remain fully occluded at theconstriction site 8, the fluid continues to accumulate inside tubes 9and in that part of tube 7 which lies between point 6 and theconstriction site 8, and the pressure transducer 17 thus displays acontinuously rising fluid pressure. The moment the block at theconstriction site 8 is partially released, the fluid escapes in the formof a jet through the partially open constriction opening 8 in thedirection of point 3. With the constriction opening 8 being onlypartially blocked, if the pump 5 continues to rotate at a constantrotational speed, the fluid pressure ultimately gets stabilized at afixed value provided the internal diameter of the constriction site 8 isnot further varied. The diameter D of the constriction site 8 rangesfrom a minimum non-zero value to a maximum value which is less than theoverall diameter of the rest of the housing tube. Thus, in thisapplication, the inner diameter of the constriction site 8 shall bedeemed to be fixed at some predetermined value D, unless otherwisestated. The fluid being displaced by the peristaltic pumps is actuallypulsatile in nature, thus the fluid pressure exhibits minute pulsationshaving a fixed frequency and a fixed amplitude. From a practical pointof view, such minute pressure fluctuations of such a regular nature canbe ignored in context with distension of body tissue cavities inendoscopic procedures. Thus, in the entire application, the fluidpressure shall be assumed to be non-fluctuating in nature.

Referring to FIG. 6, this figure is similar to FIG. 4 but a limitedregion of the irrigation circuit having an almost same pressure has beenshaded black. Due to frictional resistance experienced by the movingfluid the pressure at point 6, as sensed by the transducer 17, is alwaysfound to be higher than the actual pressure inside the tissue cavity 18but the pressure difference is so small that it may be neglected fromthe practical surgical point of view. Also, such pressure differenceincreases as the fluid flow rate increases. The term “out flow rate”refers to the flow rate of pump 14. Also, the pressure differenceremains constant all through surgery at any fixed outflow rate. Thoughthe pressure difference is negligible, if desired, its effect can alsobe totally negated by subtracting its value from the pressure reading ofthe transducer. In this manner, in endoscopic surgeries, it is possibleto determine the actual cavity pressure by using the pressure transducer17 located far away from the cavity. This feature is of specialrelevance because, in endoscopic procedures like hysteroscopy,arthroscopy and brain endoscopic surgery, it is important to know theactual cavity pressure but at the same time it is practically difficultto take a pressure measurement directly from the cavity.

Referring to FIG. 4, it shall be first described as to how the systemcan be used mechanically, that is without a controller. The peristalticpumps 5 and 14 can be made to work at any fixed rotational speed and thefluid flow rate of each pump is directly proportional to the pump RPM orthe pump rotational speed. Thus, any precise pump flow rate can begenerated by selecting a suitable pump rotational speed. The fluid flowrate of pump 14 shall henceforth be denoted by R2 and shall be termed asthe “outflow rate.” The fluid flow rate of pump 5 shall be denoted by R1and shall be termed as the “inflow rate.” Here, it is to be noted thatthe term “inflow rate” R1 is not the true inflow rate for the cavity 18,as might be suggested by the literary meaning of the term “inflow”because R1 is not the actual rate at which fluid into the cavity 18because some fluid also constantly escapes through the constriction siteopening 8. Thus, the term “inflow rate” refers to the flow rate of theinflow pump 5 unless specifically mentioned. However, the term “outflowrate” R2 does correspond to the literary meaning of the term “outflow”because R2 is equal to the rate at which fluid flows out of the cavity18. The surgeon initially decides an outflow rate R2 by selecting asuitable rotational speed for pump 14. Next, the surgeon decides themaximum flow rate at which fluid could be allowed to enter into thecavity via the inflow tube 10 and the inflow pump 5 is set to work atsuch flow rate or at a flow rate slightly lesser than this.Intravasation is the process by which fluid enters into the patient'sblood circulation through the cut ends of blood vessels located in thecavity wall or enters into the patient's body, for example into theperitoneal cavity, as a result of an accidental perforation or escapesvia patent fallopian tubes into the peritoneal cavity. Thus,“intravasation” is a process by which the pressurized irrigation fluidenters into the patient's body system through the walls of the tissuecavity. In case of a surgical accident, like cavity wall perforation,the fluid being pumped by the inflow pump 5 can enter into the patient'sbody at a rate almost equal to R1. It is obvious that the maximum rateof fluid intravasation cannot exceed the value R1. In case of anaccident, like cavity wall perforation, it may take some time before anabnormally high intravasation rate is discovered and in such time adangerous quantity of fluid might enter into the patient's body. If theinflow rate R1 is kept at a relatively lower value then the volume ofintravasated fluid in case of such an accident would be low. Afterfixing the values for R2 and R1, the system is started and the diameterof the constriction site 8 is gradually reduced. As the diameter of theconstriction site 8 is reduced, fluid starts flowing into the tissuecavity and the pressure inside the tissue cavity starts rising. When thedesired pressure is achieved inside the tissue cavity, the diameter ofthe constriction site 8 is not reduced any further and is fixed. Thediameter of the constrictions site at this stage is termed as “D”. Theconstriction site may also be a plastic or metal piece which has a holein the centre such that the diameter of the hole is permanently fixed atsome value D. If a constriction 8 has a permanently fixed diameter thenonly the flow rates of pumps 14 and 5 have to be set before the systembecomes completely operational.

The inventors here would like to discuss the importance of incorporatingthe housing tube 7 with the constriction site and the non-obviousadvantages provided by the housing tube 7 with the constriction site.

The surgeons have only two options, either to ignore cavity pressurevariations by not correcting them, or to externally and actively correctsuch pressure variations. To externally and actively correct thevariations in the cavity pressure, a controller is generallyincorporated and the working of the pumps is essentially controlled bythe controller. Incorporation of the controller controlling theoperation of the pumps does not provide any benefit. The controlleractivates the controlling action after the variations in the cavitypressure have subdued. Thus, the controlling action initiated by thecontroller instead of benefiting the surgeon leads to an undesirableturbulence inside the cavity and also tends to amplify the resultantmovement excursions of the cavity walls.

The inventors have noticed that if the controller continuously controlsthe operations of the pumps (either on the inflow side or on the outflowside), the cavity pressure continuously fluctuates around a preset valueand it is not possible to attain a constant value. The Inventors believethat the controller provides proper corrective action (by continuouslycontrolling the operations of the pumps) only if the fluctuations in thecavity pressure are gradual and not highly instantaneous. That is, ifthe quantitative rise/fall in the cavity pressure is over long timeperiod, the controller would be able to provide proper correctiveaction. As the time period to detect variation in the cavity pressureand commence corrective action is ideally in the range of 2 to 4seconds, if the quantitative rise/fall in the cavity pressure is oververy short time period, the suggested mechanism of providing acontroller will be unsuitable. Under such instances, instead ofproviding any corrective action, the controller destabilizes the systemand induces additional pressure fluctuations inside the cavity (becauseof commencing a corrective action at a delayed stage). Thus, it takesvery long time period for the system to once again get stabilized.

The inventors have surprisingly found that incorporation of a housingtube provided with a constriction site at the inflow side as describedabove inherently and passively corrects the pressure variations due tophysiological cavity wall contractions and the mechanical movement ofthe tubes and the endoscope, and also limits the variation in the sizeof the cavity. The applicants highlight that it is important to controlboth the variations in the pressure inside the cavity and the changes inthe size of the distended cavity. Large variations in the pressureinside the cavity or the size of the cavity are detrimental to thesurgical procedure. During the contraction of the cavity, a minutequantity of the fluid is pushed out of the cavity. If during this stagethe system does not provide a way for releasing the fluid being pushedout, the instantaneous pressure inside the cavity increases tremendouslywhich is harmful to the patient. On the other hand, if the amount offluid being pushed out of the cavity is not checked or controlled, thechanges in the size of the distended cavity are very high. Theincorporation of the housing tube having the constriction site in thepresent system controls both the variations in the pressure inside thecavity and the changes in the size of the distended cavity. The housingtube having the constriction site provides a by-pass route for the fluidbeing pushed out of the cavity to go back to the fluid supply tube orthe fluid source reservoir. This avoids the instantaneous pressure surgeinside the cavity which is harmful to the patient. The size of thediameter at the constriction site automatically controls the amount offluid passing through the housing tube, thereby controlling the amountof fluid being pushed out of the cavity. Inclusion of the housing tubewith the constriction site therefore minimizes the instantaneousvariations in the size of the distended cavity.

Alternatively, if the cavity expands, a suitable volume of fluid issucked into the cavity from the irrigation circuit, such as from theregion of point 6. This is accompanied by a corresponding transientdecrease in the flow rate at which fluid which fluid is escaping via theconstriction site 8 in the direction of point 3 but if the magnitude ofthe physiological expansion is more fluid may even be sucked into thecavity via the constriction site 8. This implies that the constrictionsite 8 is helping in maintaining a stable cavity pressure despitephysiological cavity wall contractions by suitably varying the magnitudeof an imaginary fluid flow vector passing through the constriction site8.

Determining the Real Time Rate of Fluid Intravasation

Referring to FIG. 4, let it be hypothetically assumed that the diameterat the constriction site 8 has been fixed at some predetermined value D,the outflow and the inflow rates have been fixed at some values R2 andR1 respectively and in such a situation a pressure P is created insidethe tissue cavity 18 when the system is operated. In such case, if nointravasation occurs during the endoscopic procedure then the pressureinside the tissue cavity 18 continues to remain at the same value P.However, if at any stage during the endoscopic procedure intravasationoccurs, then the cavity pressure immediately falls below the desiredinitial value P and inflow rate has to be increased by some magnitude inorder to raise the cavity pressure to its initial value P. Here,magnitude of the required increase in the inflow rate to attain theinitial cavity pressure P is equal to the instantaneous real time rateof intravasation R3 existing at that moment of time. In this way, thereal time rate of fluid intravasation can be determined by using themechanical version of the system.

Cavity Pressure or the Outflow Rate, Both can be Altered Independentlywithout Varying the Value of the Other Parameter

Referring again to FIG. 4, a hypothetical endoscopic procedure is beingconsidered where surgery is being performed at an outflow rate R2 andinflow rate R1 with the constriction 8 diameter being been fixed at somevalue D and a resultant cavity pressure P being created maintained. Insuch hypothetical situation, as long as R2 and R1 are not altered, thecavity pressure P remains predictably constant throughout surgeryresulting in a predictably stable mechanical distension of the tissuecavity walls which culminates in constant clear visualization throughoutthe endoscopic procedure. If in the hypothetical procedure the cavitypressure needs to be increased without altering the out flow rate R2,then all that is needed is to start increasing the value of R1 and stopdoing so when the desired higher cavity pressure is achieved. Similarly,if the cavity pressure needs to be decreased without altering the outflow rate R2 then R1 is decreased till the desired lower cavity pressureis attained. In the hypothetical endoscopic procedure, if the outflowrate R2 needs to be increased without altering the cavity pressure P,then the value of R2 is increased by the desired magnitude butsimultaneously the value of R1 is also increased by a similar magnitude.Similarly, if the outflow rate R2 needs to be decreased without alteringthe cavity pressure P, then the value of R2 is decreased by the desiredmagnitude but simultaneously the value of R1 is also decreased by asimilar magnitude. Thus, if R1 and R2 are simultaneously increased ordecreased by the same magnitude the cavity pressure does not vary, andthe value D is always fixed as already stated.

The preceding statements shall now be explained by the help of anumerical hypothetical example. In reference to FIG. 4, considering ahypothetical situation in which an endoscopic procedure is being done atan outflow rate of 100 ml/minute, an inflow rate R1 and the cavitypressure being 80 mm Hg. If the surgeon wants to increase the outflowrate to 322 ml/minute by maintaining the cavity pressure at the samevalue of 80 mm Hg, the outflow rate is increased to 322 ml/minute andthe inflow rate is increased by 222 ml/minute, because 322 ml/min−100ml/min=222 ml/minute. As already mentioned, if both inflow and outflowrates are increased or decreased by the same magnitude, the cavitypressure does not change. Thus, the final inflow rate becomes R1+222ml/minute, where R1 was the initial inflow rate. Thus, in the proposedsystem of the present invention, the cavity pressure and the outflowrate both can be altered absolutely independent of each other withoutaffecting the value of the other parameter.

Mechanical Version of the System

The mechanical version of the system shown in FIG. 4 can be usedpractically in endoscopic surgeries but it requires a human operator.Thus, the controller based version of the system shall be discussed insubsequent paragraphs.

Controller Based Version of the System

Referring to FIG. 3, this figure shows a schematic diagram of the systemwith a controller. FIG. 3 and FIG. 4 are similar except that in FIG. 4the controller system is not included. A tachometer, not shown in thediagrams, is coupled to each peristaltic pump and sends informationregarding the pump rotation speed to the controller 19 via wires 20 and23. The pump flow rates being proportional to the pump rotation speed,the tachometer signal always conveys flow rate related information tothe controller. As already mentioned, both peristaltic pumps have beenconsidered to be similar in all respects because this makes it easier tounderstand and operate the system. However, the two peristaltic pumpsmay also be different in context with the inner diameter of theperistaltic pump tubes 4 and 13 but in such case suitable modificationshave to be made in the controller programming in order to operate thesystem as described in this manuscript. The controller also regulatesthe rotation speed of the two pumps via electrical signals sent throughwires 24 and 21. The pressure transducer 17 conveys the pressure signalto the controller via wires 22. On the basis of a pressure feed backsignal received from the pressure transducer 17 the controller regulatesthe rotational speed of the inflow pump 5. The outflow pump 14 works atfixed outflow rates and the flow rate of this pump is also regulated bythe controller via suitable electrical signals sent via wires 21. Aprovision exists by which desired values for P and R2 can be fed intothe controller and the values R1, R2 and P can be continuously displayedvia suitable display means incorporated in the controller. Thecontroller can be programmed to perform many special functions relatedto endoscopic surgery which shall be discussed in the followingparagraphs.

Method of Operating the Controller Based Version of the System

Referring to FIG. 3, in context with the system at the start of surgerythe surgeon initially selects suitable values for cavity pressure P andoutflow rate R2. The desired values of P and R2 are fed into thecontroller via suitable input means incorporated in the controller. Thediameter D at the constriction site 8 remains fixed at some pre selectedvalue. The diameter of the constriction site 8 is so chosen that itsuits the operational needs of the endoscopic procedure. The method ofselecting a suitable diameter D for the constriction site 8 has alreadybeen discussed under the heading “Selection of a suitable diameter forthe constriction site.” When the system shown in FIG. 3 is operated, thecontroller 19 instructs the outflow pump 14 via wires 21 to continuouslyextract fluid out of the body cavity 18 at a desired fixed outflow rateR2. Thus, all through the surgery, the outflow rate remains fixed at R2irrespective of any internal or external factors unless intentionallychanged by the surgeon. The cavity pressure is sensed by the pressuretransducer 17 and a corresponding pressure feedback signal is sent tothe controller via wires 22 on the basis of which the controllerregulates the inflow rate R1, via wires 24. After the system is madeoperational the controller 19 gradually increases the inflow rate up tothe point where the desired preset cavity pressure P is achieved. Letthe value of the inflow rate at which the desired cavity pressure isachieved be termed as “R1. final.” It is obvious that the value“R1.final” is actually determined by the controller by a pressure feedback mechanism and such determination of the value is based on thepreset values of R2 and P. The controller is so programmed that once thevalue “R1.final” is achieved and is maintained for a desired minimumtime interval, for example 10 seconds, after which the controllerreleases the inflow pump 4 from its pressure feedback control mechanismand allow the inflow pump 4 to operate on its own at an inflow rate“R1.final” which was determined by the controller. In this manner, thetwo peristaltic pumps continue to work at fixed flow rates to maintain adesired stable cavity pressure. The controller is also programmed thatin case the cavity pressure subsequently alters, for example due tointravasation, by a desired minimum preset magnitude and for a desiredminimum time, which may hypothetically be 10 seconds, the inflow pump 4again comes under the pressure feedback control of the controller and anew value of “R1.final” is determined by the controller after which theinflow pump 4 is again allowed to be operated without the pressurefeedback mechanism at the newly determined “R1.final” inflow rate. Suchsequences of events continue to occur throughout the endoscopicprocedure. Taking an imaginary example, if the total surgical time is 60minutes then it may be hypothetically possible to operate the inflowpump independent of the pressure feedback mechanism for 55 minutes andunder the control of the pressure feedback mechanism for 5 minutes.However, provision of operating the inflow pump 4 under a pressurefeedback mechanism all through the endoscopic procedure can also beincorporated.

The Advantage of Operating the Inflow Pump Independent of the PressureFeedback Mechanism

One reason for operating the inflow pump 4 independent of the pressurefeedback mechanism is to avoid unnecessary corrections of minor pressurevariations caused by physiological cavity wall contractions. In thepresent system, the physiological variations in cavity pressure areautomatically corrected by the constriction site 8 without the need of acontroller. If the cavity contracts a minute quantity of fluid which ispushed out of the cavity escapes via the constriction site 8 towardspoint 3. It is noted that the part of tube 7 between point 8 and 3 is atatmospheric pressure, thus the fluid which is expelled from the cavityas a result of a physiological contraction escapes through theconstriction site 8 against a zero pressure head, which is atmosphericpressure. Thus, the transient, insignificant and instantaneous rise andfall in cavity pressure gets stabilized at the desired preset valuewithin a fraction of seconds. Alternatively, if the cavity expands asuitable volume of fluid is sucked into the cavity from the irrigationcircuit, such as from the region of point 6, and this is accompanied bya corresponding transient decrease in the flow rate at which fluid isescaping via the constriction site 8 in the direction of point 3 but ifthe magnitude of the said physiological expansion is more fluid may evenbe sucked into the cavity via the constriction site 8. This implies thatthe constriction site 8 is helping in maintaining a stable cavitypressure despite physiological cavity wall contractions by suitablyvarying the magnitude of an imaginary fluid flow vector passing throughthe constriction site 8. Normally, the direction of such imaginaryvector is always towards point 6 while its magnitude constantly variesto take care of the pressure changes resulting due to physiologicalcavity contractions. Normally, a cavity continuously contracts anddilates by approximately the same magnitudes, thus there is no logic tocheck the minor pressure variations emanating from the saidcontractions. Also, the opening of the constriction site 8 does notallow the said physiological cavity pressure fluctuations to cause anysignificant cavity wall movement excursions by allowing to and fromovement of flow through its lumen. However, if the pressure changes aremade to be corrected by a controller, as is done in the prior artsystems, the cavity wall may exhibit significant irregular pressurefluctuations which may result in significant movement excursions of thecavity wall, thus disallowing a predictably stable mechanicalstabilization of the cavity walls. However, in the eventuality of fluidintravasation the fall in cavity pressure drop is relatively morepermanent in nature thus needs to be corrected by the controller. Asalready explained, the controller is so programmed that the inflow pump4 automatically comes under the pressure feedback control mechanism ofthe controller in case the cavity pressure alters by a desired minimumpreset magnitude and for a desired preset time interval, thus a new“R1.final” inflow rate is established at which the inflow pump is againallowed to operate without the feedback control of the controller. As asafety precaution, a provision can be made in the controller viasuitable input means to fix an upper safe limit for the inflow rate R1and the cavity pressure P such that these safe limits are not exceededaccidentally.

Controller Programming for Determining the Instantaneous Rate of FluidIntravasation During Surgery

In the above paragraphs a mechanical method of determining theinstantaneous real time instantaneous rate of fluid intravasationwithout using the controller has been described. However, suchmechanical evaluation is subject to human error and is also difficult torepeat multiple times during an endoscopic procedure. Hence, the needarises to continuously determine and display the real time rate of fluidintravasation by the help of the controller. Excess fluid intravasationduring an endoscopic procedure can even lead to the patient's death thusit is extremely important for the surgeon to reliably, accurately andconstantly know the real time rate of fluid intravasation R3 throughoutthe endoscopic procedure. In order to determine the real time rate ofintravasation, an equation KP=(R1−(R2+R3))² has been derived whereK=constant, P=cavity pressure, R1=inflow rate, R2=outflow rate andR3=instantaneous rate of fluid intravasation. In the equation, thevalues of P, R1 and R2 are always known by the controller and the valueof the constant K can be determined by suitable analytical means. Thus,in the equation, R3 is the only unknown value which can be determined byfeeding the expression contained in the equation into the controller viasuitable programming means and directing the controller to continuouslydetermine and display R3. The controller can be further programmed tocarry out multiple other functions related to intravasation, such as analarm being sounded if intravasation of a specific minimum magnitudeoccurs or if the rate of intravasation rate increases by a specificmagnitude. The controller can also be programmed to completely shut downthe system in case the rate of intravasation exceeds a specifieddangerously high rate.

Selection of a Suitable Diameter for the Constriction Site

If the diameter of the constriction site 8 is very small, then thetransient pressure fluctuation in the cavity pressure would be of arelatively larger magnitude and would last for a relatively longer timeinterval but the associated resultant movement excursion of the cavitywall would be of a relatively small amplitude. Similarly, if thediameter of the constriction site 8 is very large, then the transientcavity pressure fluctuations would be of a relatively smaller magnitudeand would last for a relatively shorter time interval, but theassociated resultant movement excursion of the cavity walls would be ofmuch larger amplitude. These statements are explained by the help ofthree hypothetical numerical assumptions as stated in table 1 which isas follows:

TABLE 1 A hypothetically assumed numerical value of the magnitude of atransient A A A pressure surge associated hypothetically assumedhypothetically assumed hypothetically assumed with a physiological timeinterval for which magnitude of the Serial number numerical value of thecavity wall contraction the said pressure surge associated resultantcavity of the assumption constriction site diameter movement exists wallmovement excursion 1 0.1 mm 20 mm Hg  3 seconds 0.5 mm 2   1 mm 5 mm Hg1 second 1 mm 3 1.5 mm 1 mm Hg 0.5 seconds 5 mm Hg (*Note: A similartable can be hypothetically constructed taking into consideration cavitywall expansion, instead of contraction.)

In context of routine endoscopic procedures, the above mentionedhypothetical situation associated with serial number 2 is mostacceptable out of the three hypothetical examples because a highmagnitude cavity wall movement excursion is not at all desirable while amoderately high transient pressure surge may be acceptable in mostendoscopic procedures. Thus, the nuisance value of a cavity wallmovement excursion is relatively more than the nuisance value of thesaid transient pressure surge. However, the amplitude of the pressuresurge should also be not very high because it may promote intravasationand other problems.

Thus, while selecting the diameter of the constriction site, two thingsare kept in mind, the operational needs of the endoscopic procedure asalready explained in this paragraph and the anticipated cavity wallcontraction and expansion movements. Thus, in those endoscopicprocedures where mechanical stability of the cavity walls is important,the numerical value of the constriction site diameter D should berelatively smaller.

Referring to FIGS. 3 to 7, the inflow tube 10 and the outflow tube 12have been shown connected to the inlet and the outlet openings of acavity 18 however such description is proposed only for the sake of aneasier understanding of the system. In actual practice, the distal endof the inflow tube 10 is connected to an inflow port of a “continuousflow endoscope” and the proximal end of the outflow tube is connected tooutflow port of the “continuous flow endoscope.”

In the subsequent paragraphs the advantages and method of attaching andusing the endoscope 27 with the described fluid management system shallbe discussed.

The Advantages and the Method of Attaching the Endoscope with the FluidManagement System

FIG. 1 shows the main block diagram of the invention. FIG. 1 is similarto FIG. 3 except that the tissue cavity 18 has been substituted by theendoscope 27. Though tissue cavity 18 has not been included in thisfigure, it is deemed to be understood that the distal end of theendoscope 27 is has been inserted via a single natural or a singlecreated opening in the cavity. The distal open end of the inflow tube 10has been shown connected to the inflow port 33 of the endoscope 27. Theproximal open end of the outflow tube 12 has been connected to theoutflow port 42 of the endoscope 27.

The fluid management system as described in FIGS. 3, 4, 6 and 7 removesfluid from the tissue cavity 18 by a process of active extraction andnot by passive expulsion and such arrangement prevents the cavity 18from collapsing despite the relatively large lumen diameter of theoutflow port 42.

The arrangement shown in FIG. 1 provides a system of distending a bodytissue cavity by continuous flow irrigation such that the detachedtissue pieces and waste fluid present inside the cavity 18 iscontinuously evacuated via a single same outflow port 42 without theneed of withdrawing the endoscope or a part of the endoscope, such asthe endoscopic instrument, from the tissue cavity. The evacuated tissuepieces and the waste fluid is finally transported to the waste fluidcollecting container 16 via the outflow tube 12 and the waste fluidcarrying tube 45. Such an arrangement as shown in FIG. 1 also providesother benefits such as maintaining constant clear endoscopicvisualization of the interior of the cavity, maintaining a constantcavity pressure and maintaining a constant mechanical distention of thecavity. The most important, especially in context with the inventedsystem, is that the tissue cavity does not collapse despite a relativelylarge lumen diameter of the instrument 32 and the outflow port 42.Besides these benefits, the arrangement of FIG. 1 provides multipleother benefits such as determining the real time rate of fluidintravasation. In FIG. 1, in case the outflow pump 14 is removed and thedistal end of the outflow tube 12 is made to open directly in atmospherethe cavity would tend to collapse intermittently during an endoscopicprocedure, and such an arrangement as seen in the prior art systems hasbeen described in the previous paragraph as “passive expulsion.”

Referring to FIG. 1, a remote possibility could be proposed wherein thedetached tissue pieces block the lumen 41 or the outflow port 42 of theinstrument 32. In case of the remote possibility the outflow pump 14, orpreferably both pumps 14, 5 could be made to rotate simultaneously in anopposite direction, that is in a direction opposite to the direction ofthe curved arrows, at a relatively high flow rate and for a relativelyshort period of time and such action is being termed as “flushingmaneuver.” The “flushing maneuver” would immediately flush the blockingtissue back into the tissue cavity and normal surgery could continueafter this. The “flushing maneuver” could be initiated manually by thesurgeon for example by a foot switch. The “flushing maneuver” could alsobe initiated by the help of a “pressure feedback mechanism” which wouldrequire an appropriate programming of the controller. The “pressurefeedback mechanism” could utilize the optional outflow pressuretransducer 26, or both the pressure transducers 26 and 17.

The endoscope 27 has been included in FIG. 1 but it is also deemed to beincluded in FIGS. 3, 4, 6 and 7 as well.

Referring to FIG. 1, both pumps, 5 and 14, and the endoscope 27 work ina synergistic manner such that both enhance the efficiency of either.

The invention is useful since it enhances the patient safety andsurgical efficiency in continuous flow irrigation based endoscopicprocedures.

Although the present invention has been described in connection withpreferred embodiments, many modifications and variations will becomeapparent to those skilled in the art. While preferred embodiments of theinvention have been described and illustrated above, it should beunderstood that these are exemplary of the invention and are not to beconsidered as limiting. Accordingly, it is not intended that the presentinvention be limited to the illustrated embodiments, but only by theappended claims.

1. A continuous flow irrigation system, comprising: an endoscopecomprising an outer sheath having a longitudinal axis, a distal end anda proximal end; an inflow port located at the proximal end of the outersheath, configured to allow fluid to enter the outer sheath; a tubeextending about parallel to the longitudinal axis of the outer sheath,the tube being configured to move in at least one of a linear motion anda rotary motion relative to the longitudinal axis of the outer sheath;and an outflow port located at a proximal end of the tube; an inflowpump connected to the inflow port of the endoscope; and an outflow pumpconnected to the outflow port of the endoscope.
 2. The system of claim1, wherein at least one of the inflow pump and the outflow pump is aperistaltic pump, piston pump, gear pump or diaphragm pump.
 3. Thesystem of claim 1, wherein the inflow pump is connected to a fluidsource reservoir, and wherein the system further comprises a second tubehaving a variable size constriction site provided between the fluidsource reservoir and the inflow port of the endoscope, the second tubeproviding a route for any excess fluid being pumped by the inflow pumpto bypass the inflow pump.
 4. The system of claim 1, wherein the tube ofthe endoscope is an inner channel of a surgical instrument and also anevacuation channel for fluid and/or tissue debris from a tissue cavity.5. The system of claim 4, wherein the surgical instrument is selectedfrom the group consisting of a morcellator, shaver, cutter, electrodeand electrosurgical instrument.
 6. The system of claim 1, furthercomprising a pressure transducer for sensing the pressure of fluidentering the inflow port of the endoscope.
 7. The system of claim 1,wherein the endoscope further comprises an optical channel, at least aportion of the optical channel being non-parallel to the longitudinalaxis of the outer sheath.
 8. The system of claim 1, wherein theendoscope further comprises an optical channel about parallel to thelongitudinal axis of the outer sheath.
 9. The system of claim 1, whereinthe outflow port of the endoscope is located outside the outer sheath.10. A continuous flow irrigation system for an endoscopic procedure, thesystem comprising: an endoscope comprising a tubular outer housinghaving a longitudinal axis, a distal end and a proximal end; an inflowport located at the proximal end of the tubular outer housing,configured to allow fluid to enter the tubular outer housing; an opticschannel located within the tubular outer housing and comprising a bentregion that forms an angle relative to the longitudinal axis of thetubular outer housing; a movable tube extending about parallel to thelongitudinal axis of the tubular outer housing, the movable tube beingconfigured to move in at least one of a linear motion and a rotarymotion relative to the longitudinal axis of the tubular outer housing;and an outflow port located at a proximal end of the movable tube; afirst peristaltic pump connecting a fluid source reservoir to the inflowport of the endoscope via an inflow tube; a second peristaltic pumpconnecting a waste fluid reservoir to the outflow port of the movabletube of the endoscope; and a tube having a controllable constrictionsite provided between the fluid source reservoir and the inflow port ofthe endoscope, the tube providing a route for any excess fluid beingpumped by the first peristaltic pump to bypass the first peristalticpump.
 11. The system of claim 10, wherein the fluid source reservoircontains a non-viscous physiologic fluid maintained at atmosphericpressure or a pressure greater than the atmospheric pressure.
 12. Thesystem of claim 10, wherein the movable tube of the endoscope is aninner channel of a surgical instrument selected from the groupconsisting of morcellator, shaver, cutter, electrode and electrosurgicalinstrument.
 13. The system of claim 10, wherein the movable tube of theendoscope is an inner channel of a ball electrode.
 14. The system ofclaim 10, wherein the endoscopic procedure is selected from the groupconsisting of hysteroscopic fibroid morcellation, trans uretheralprostate morcellation, hysteroscopic polyp morcellation, hysteroscopicseptoplasty, hysteroscopic adhesiolysis, trans uretheral morcellation ofbladder tumors, and arthroscopy.
 15. A method of continuous flowirrigation during an endoscopic procedure, comprising the steps of:providing a continuous flow irrigation endoscope in the vicinity of atissue cavity, the endoscope comprising an outer sheath having alongitudinal axis, a distal end and a proximal end; an inflow portlocated at the proximal end of the outer sheath, configured to allowfluid to enter the outer sheath; a tube extending about parallel to thelongitudinal axis of the outer sheath, the tube being configured to movein at least one of a linear motion and a rotary motion relative to thelongitudinal axis of the outer sheath; and an outflow port located at aproximal end of the tube; connecting the inflow port of the endoscope toa fluid source via an inflow pump for pumping fluid from the fluidsource at a controlled inflow rate into the inflow port of the endoscopeand the tissue cavity, wherein the inflow rate is the flow rate of theinflow pump; and connecting the outflow port of the endoscope to anoutflow pump for removing waste fluid from the tissue cavity at acontrolled outflow rate, wherein the outflow rate is the flow rate ofthe outflow pump.
 16. The method of claim 15, further comprising thestep of providing a second tube having a controllable constriction sitebetween the inflow port of the endoscope and the fluid source reservoirsuch that the second tube provides a route for any excess fluid beingpumped by the inflow pump or due to the physiologic contraction of wallsof the body cavity, therefore avoiding turbulence inside the body cavityand maintaining a stable pressure inside the body cavity.
 17. The methodof claim 15, wherein the endoscopic procedure is selected from the groupconsisting of hysteroscopic fibroid morcellation, trans uretheralprostate morcellation, hysteroscopic polyp morcellation, hysteroscopicseptoplasty, hysteroscopic adhesiolysis, trans uretheral morcellation ofbladder tumors, and arthroscopy.
 18. The method of claim 15, wherein theinflow rate and the outflow rate are simultaneously increased ordecreased without altering the pressure inside the tissue cavity.
 19. Amethod of controlling pressure variations within a body tissue cavityduring an endoscopic procedure, comprising the steps of: providing acontinuous flow irrigation endoscope at least partially within a tissuecavity, the endoscope comprising only an outer sheath without an innersheath, the outer sheath having a longitudinal axis, a distal end and aproximal end; an inflow port located at the proximal end of the outersheath, configured to allow fluid to enter the outer sheath; a tubeextending about parallel to the longitudinal axis of the outer sheath;and an outflow port located at a proximal end of the tube; providing aninflow peristaltic pump in communication with the inflow port of theendoscope, to provide fluid into the tissue cavity; providing an outflowperistaltic pump in communication with the outflow port of theendoscope, to remove fluid from the tissue cavity through the tube ofthe endoscope; selecting an outflow rotational speed for the outflowperistaltic pump; selecting a maximum flow rate at which fluid entersthe tissue cavity and, based on the maximum flow rate, selecting aninflow rotational speed for the inflow peristaltic pump; activating theinflow peristaltic pump and the peristaltic outflow pump, to allow fluidto flow through the inflow port of the endoscope and into the tissuecavity, and from the tissue cavity through the outflow port of theendoscope, so that pressure inside the tissue cavity rises to a setpressure cavity; and maintaining the set pressure cavity for a period oftime.
 20. The method of claim 19, wherein the step of maintaining theset pressure cavity for a period of time is achieved by simultaneouslyincreasing the inflow rotational speed and the outflow rotational speedby same numerical amount.
 21. The method of claim 19, wherein the stepof maintaining the set pressure cavity for a period of time is achievedby simultaneously decreasing the inflow rotational speed and the outflowrotational speed by same numerical amount.
 22. The method of claim 19,wherein the set pressure cavity is independently maintained from theinflow rotational speed and the outflow rotational speed.
 23. The methodof claim 19, further comprising the step of providing a constrictiontube having a controllable constriction site between the inflow port ofthe endoscope and the inflow pump such that the constriction tubeprovides a route for any excess fluid being pumped by the inflow pump ordue to the physiologic contraction of walls of the body cavity,therefore avoiding turbulence inside the body cavity and maintaining astable pressure inside the body cavity.
 24. The method of claim 23,further comprising the step of gradually reducing the diameter of thecontrollable constriction site to a fixed diameter until the setpressure cavity is achieved.
 25. The method of claim 19, wherein thetube of the endoscope is an inner channel of a surgical instrumentselected from the group consisting of morcellator, shaver, cutter,electrode and electrosurgical instrument.